Managing reforestation to sequester carbon, increase biodiversity potential and minimize loss of agricultural land

Reforestation will have important consequences for the global challenges of mitigating climate change, arresting habitat decline and ensuring food security. We examined field-scale trade-offs between carbon sequestration of tree plantings and biodiversity potential and loss of agricultural land. Extensive surveys of reforestation across temperate and tropical Australia (N=1491 plantings) were used to determine how planting width and species mix affect carbon sequestration during early development (< 15 year). Carbon accumulation per area increased significantly with decreasing planting width and with increasing proportion of eucalypts (the predominant over-storey genus). Highest biodiversity potential was achieved through block plantings (width>40m) with about 25% of planted individuals being eucalypts. Carbon and biodiversity goals were balanced in mixed-species plantings by establishing narrow belts (width<20m) with a high proportion (>75%) of eucalypts, and in monocultures of mallee eucalypt plantings by using the widest belts (ca. 6-20m). Impacts on agriculture were minimized by planting narrow belts (ca. 4m) of mallee eucalypt monocultures, which had the highest carbon sequestering efficiency. A plausible scenario where only 5% of highly-cleared areas (<30% native vegetation cover remaining) of temperate Australia are reforested showed substantial mitigation potential. Total carbon sequestration after 15 years was up to 25Mt CO2-e year-1 when carbon and biodiversity goals were balanced and 13Mt CO2-e year-1 if block plantings of highest biodiversity potential were established. Even when reforestation was restricted to marginal agricultural land (<$2000ha-1 land value, 28% of the land under agriculture in Australia), total mitigation potential after 15 years was 17-26Mt CO2-e year-1 using narrow belts of mallee plantings. This work provides guidance on land use to governments and planners. We show that the multiple benefits of young tree plantings can be balanced by manipulating planting width and species choice at establishment. In highly-cleared areas, such plantings can sequester substantial biomass carbon while improving biodiversity and causing negligible loss of agricultural land.

Integrating plant- and animal- based perspectives for more effective restoration of biodiversity

Ecological restoration of modified and degraded landscapes is an important challenge for the 21st century, with potential for major gains in the recovery of biodiversity. However, there is a general lack of agreement between plant- and animal- based approaches to restoration, both in theory and practice. Here, we review these approaches, identify limitations from failing to effectively integrate their different perspectives, and suggest ways to improve outcomes for biodiversity recovery in agricultural landscapes. We highlight the need to strengthen collaboration between plant and animal ecologists, to overcome disciplinary and cultural differences, and to achieve a more unified approach to restoration ecology. Explicit consideration of key ecosystem functions, the need to plan at multiple spatial and temporal scales, and the importance of plant-animal interactions can provide a bridge between plant- and animal- based methods. A systematic approach to restoration planning is critical to achieving effective biodiversity outcomes while meeting long- term social and economic needs.

Designer policy for carbon and biodiversity co-benefits under global change

Carbon payments can help mitigate both climate change and biodiversity decline through the reforestation of agricultural land. However, to achieve biodiversity co-benefits, carbon payments often require support from other policy mechanisms such as regulation, targeting, and complementary incentives. We evaluated 14 policy mechanisms for supplying carbon and biodiversity co-benefits through reforestation of carbon plantings (CP) and environmental plantings (EP) in Australia's 85.3 Mha agricultural land under global change. The reference policy - uniform payments (bidders are paid the same price) with land-use competition (both CP and EP eligible for payments), targeting carbon - achieved significant carbon sequestration but negligible biodiversity co-benefits. Land-use regulation (only EP eligible) and two additional incentives complementing the reference policy (biodiversity premium, carbon levy) increased biodiversity co-benefits, but mostly inefficiently. Discriminatory payments (bidders are paid their bid price) with land-use competition were efficient, and with multifunctional targeting of both carbon and biodiversity co-benefits increased the biodiversity co-benefits almost 100-fold. Our findings were robust to uncertainty in global outlook, and to key agricultural productivity and land-use adoption assumptions. The results suggest clear policy directions, but careful mechanism design will be key to realising these efficiencies in practice. Choices remain for society about the amount of carbon and biodiversity co-benefits desired, and the price it is prepared to pay for them.

Analysis of trade-offs between biodiversity, carbon farming and agricultural development in northern Australia reveals the benefits of strategic planning

Australia's northern savannas are one of the few remaining large and mostly intact natural areas on Earth. However, their biodiversity and ecosystem values could be threatened if proposed agricultural development proceeds. Through land-use change scenarios, we explored trade-offs and synergies among biodiversity conservation, carbon farming and agriculture production in northern Australia. We found that if all suitable soils were converted to agriculture, habitat at unique recorded locations of three species would disappear and 40 species and vegetation communities could lose more than 50% of their current distributions. Yet, strategically considering agriculture and biodiversity outcomes leads to zoning options that could yield >56,000 km2 of agricultural development with a significantly lower impact on biodiversity values and carbon farming. Our analysis provides a template for policy-makers and planners to identify areas of conflict between competing land-uses, places to protect in advance of impacts, and planning options that balance agricultural and conservation needs.

Reforms required to the Australian tax system to improve biodiversity conservation on private land

Private land conservation forms an integral part of Australia’s natural resource management and biodiversity conservation efforts, and the past two decades have seen a significant growth in the establishment of in-perpetuity conservation covenants. Specifically, conservation covenants address key national goals such as building the National Reserve System and expanding the markets for ecosystem services. However, a number of financial barriers exist to achieving these goals, and the national tax review in the form of the Tax White Paper Task Force provides an opportunity to address these barriers. This article provides a number of specific recommendations which outline how these financial barriers for private land conservation might be addressed by the Federal Government.

Bombs and biodiversity: a case study of military environmentalism in Australia

The relationship between war, militarization, and landscapes is far more complex and nuanced than one characterized by domination and destruction. While the preparation, waging, and aftermath of war clearly have a range of negative landscape impacts, military forces are holding increasingly important, complementary roles in the defense of high conservation value sites.

Invasive predators and global biodiversity loss.

Invasive species threaten biodiversity globally, and invasive mammalian predators are particularly damaging, having contributed to considerable species decline and extinction. We provide a global metaanalysis of these impacts and reveal their full extent. Invasive predators are implicated in 87 bird, 45 mammal, and 10 reptile species extinctions-58% of these groups' contemporary extinctions worldwide. These figures are likely underestimated because 23 critically endangered species that we assessed are classed as "possibly extinct." Invasive mammalian predators endanger a further 596 species at risk of extinction, with cats, rodents, dogs, and pigs threatening the most species overall. Species most at risk from predators have high evolutionary distinctiveness and inhabit insular environments. Invasive mammalian predators are therefore important drivers of irreversible loss of phylogenetic diversity worldwide. That most impacted species are insular indicates that management of invasive predators on islands should be a global conservation priority. Understanding and mitigating the impact of invasive mammalian predators is essential for reducing the rate of global biodiversity loss.

Priorities in policy and management when existing biodiversity stressors interact with climate-change

There are three key drivers of the biodiversity crisis: (1) the well known existing threats to biodiversity such as habitat loss, invasive pest species and resource exploitation; (2) direct effects of climate-change, such as on coastal and high elevation communities and coral reefs; and (3) the interaction between existing threats and climate-change. The third driver is set to accelerate the biodiversity crisis beyond the impacts of the first and second drivers in isolation. In this review we assess these interactions, and suggest the policy and management responses that are needed to minimise their impacts. Renewed management and policy action that address known threats to biodiversity could substantially diminish the impacts of future climate-change. An appropriate response to climate-change will include a reduction of land clearing, increased habitat restoration using indigenous species, a reduction in the number of exotic species transported between continents or between major regions of endemism, and a reduction in the unsustainable use of natural resources. Achieving these measures requires substantial reform of international, national and regional policy, and the development of new or more effective alliances between scientists, government agencies, non-government organisations and land managers. Furthermore, new management practices and policy are needed that consider shifts in the geographic range of species, and that are responsive to new information acquired from improved research and monitoring programs. The interactions of climate-change with existing threats to biodiversity have the potential to drive many species to extinction, but there is much that can be done now to reduce this risk.